This invention relates to an adjustable hospital bed having a transmission for effecting a plurality of different bed adjustments at the same time, the transmission transmitting power to the adjustment mechanisms from a single common drive.
Adjustable hospital beds are usually vertically movable so that the mattress supporting structure may be established at a selected desired height, within a range of permissible heights, from the floor. The lowermost level is most convenient when a patient is entering or leaving the bed. On the other hand, the uppermost height is generally preferred for examination and treatment of the patient. To maximize the patient's comfort the mattress support is divided into a series of individually adjustable sections or panels that may be positioned, by independently operable lift mechanisms, to provide a desired contour or configuration. For example, one lift mechanism may tilt a back section so that the patient's back and head may be raised, while another lift mechanism may adjust a knee section of the mattress support to raise the patient's knees. In addition, in many adjustable hospital beds the entire mattress supporting structure may be tilted or canted to either the trendelenburg position (head down, feet up) or to the reverse trendelenburg position (head up, feet down). The bed is adjusted to the trendelenburg position when the patient goes into shock, whereas the reverse trendelenburg position is employed for drainage.
When a hospital bed has a variety of different characteristics that may be adjusted by a single common drive, such as an electric motor or a crank, a transmission has been employed in the past to couple the common drive to a selected one of a series of output shafts, such as drive screws, each of which controls a different bed adjustment or characteristic. Power may thus be transmitted to the selected output shaft to effect rotation thereof which in turn adjusts the associated bed characteristic. Since only one output shaft can be rotated at a time, when two or more different bed adjustments must be made (for example, when it is desired to raise the patient's back and knees) the adjustments must be made one at a time. One adjustment must be completed before power can be transmitted to another output shaft to make a different adjustment. Requiring sequential operation of the adjustment mechanisms extends significantly the time needed to adjust the bed. As a result, a nurse may spend a substantial amount of time adjusting a bed for a patient. Moreover, when a patient goes into shock the bed must be placed in the trendelenburg position as soon as possible. Considerable time will be lost if, for example, the back section of the mattress support must first be lowered before the entire mattress support is tilted.
In contrast, the hospital bed of the present invention also employs a single common drive for powering a variety of different adjustments but, unlike the prior systems, any combination, or even all, of these bed adjustments may be made simultaneously.